Air return ducts for heating or air conditioning systems, frequently referred to as cold air returns, are commonly located in a visible area of the floor, wall, or ceiling of a building. These air return ducts are typically covered by a cover or grille that improves the aesthetics of the duct and prevents large objects from entering the air return duct, while allowing air to flow through the duct.
Generally air return grilles comprise a single grille that can be mounted to a wall, floor, or ceiling so as to be positioned over the open end of an air return duct. This grille comprises openings that allow air to flow through the grille and into the air return duct. These grille openings are often large enough that the air return duct behind the grille is visible to a person looking at the grille, particularly in Victorian or antique style grilles where the openings are formed in a manner where the remaining material separating the openings from one another forms an ornamental pattern or design.
Various air return grille assemblies have been described. For example, U.S. Pat. No. 7,789,928 and US2007266685 disclose air duct end filter assemblies, where a frame disposed behind the main grille is used to support an air filter behind the grille, but the frame is perforated to allow airflow through it, and thus would not provide any vent-concealing functionality if used without the filter. Further, air return grilles comprising air diffuser screens supported behind the grille are available, such as those sold by Classic Grills in Valley Center, Calif., www.classicgrills.com, but the perforated screen structure of the diffuser results in openings through which an observer can see the air duct.
Grilles for air supply ducts feeding air into a room, as opposed to return air ducts receiving re-circulating air back to the furnace or air-conditioner, typically employ a damper system for opening and closing the end of the duct at which the grill is mounted. While the closed damper may obscure the grille openings, it is undesirable to provide a damper on a cold-air return grille, as unintentional closing of the damper may starve the heating/cooling system of sufficient air circulation.
Accordingly, there remains a desire for a solution for air duct concealment for ornamental air return grilles.